ObjectivesAnemia is a common complication of malignancy, which could result from either compromised erythropoiesis or decreased lifespan of circulating erythrocytes. Premature suicidal erythrocyte death, characterized by cell shrinkage and phosphatidylserine (PS) externalization, decreases erythrocyte lifespan and could thus cause anemia. Here, we explored whether accelerated eryptosis participates in the pathophysiology of anemia associated with lung cancer (LC) and its treatment.MethodsErythrocytes were drawn from healthy volunteers and LC patients with and without cytostatic treatment. PS exposure (annexin V-binding), cell volume (forward scatter), cytosolic Ca2+ (Fluo3 fluorescence), reactive oxygen species (ROS) production (DCFDA fluorescence) and ceramide formation (anti-ceramide antibody) were determined by flow cytometry.ResultsHemoglobin concentration and hematocrit were significantly lower in LC patients as compared to healthy controls, even though reticulocyte number was higher in LC (3.0±0.6%) than in controls (1.4±0.2%). The percentage of PS-exposing erythrocytes was significantly higher in LC patients with (1.4±0.1%) and without (1.2±0.3%) cytostatic treatment as compared to healthy controls (0.6±0.1%). Erythrocyte ROS production and ceramide abundance, but not Fluo3 fluorescence, were significantly higher in freshly drawn erythrocytes from LC patients than in freshly drawn erythrocytes from healthy controls. PS exposure of erythrocytes drawn from healthy volunteers was significantly more pronounced following incubation in plasma from LC patients than following incubation in plasma from healthy controls.ConclusionAnemia in LC patients with and without cytostatic treatment is paralleled by increased eryptosis, which is triggered, at least in part, by increased oxidative stress and ceramide formation.

Salinomycin, a polyether ionophore antibiotic effective against a variety of pathogens, has been shown to trigger apoptosis of cancer cells and cancer stem cells. The substance is thus considered for the treatment of malignancy. Salinomycin compromises tumour cell survival at least in part by interference with mitochondrial function. Erythrocytes lack mitochondria but may undergo apoptosis-like suicidal cell death or eryptosis, which is characterized by scrambling of the cell membrane with phosphatidylserine exposure at the erythrocyte surface. Signalling involved in the triggering of eryptosis includes activation of oxidant-sensitive Ca 2+ permeable cation channels with subsequent increase in cytosolic Ca 2+ activity ([Ca 2+ ] i ). This study explored whether salinomycin stimulates eryptosis. Phosphatidylserine-exposing erythrocytes were identified by measurement of annexin-V binding, cell volume was estimated from forward scatter, haemolysis determined from haemoglobin release, [Ca 2+ ] i quantified utilizing Fluo3-fluorescence and oxidative stress from 2 0 ,7 0 dichlorodihydrofluorescein diacetate (DCFDA) fluorescence in flow cytometry. A 48-hr exposure to salinomycin (5-100 nM) was followed by a significant increase in Fluo3-fluorescence, DCFDA fluorescence and annexin-V binding, as well as a significant decrease in forward scatter (at 5-10 nM, but not at 50 and 100 nM). The annexin-V binding after salinomycin treatment was significantly blunted but not abrogated in the nominal absence of extracellular Ca 2+ or in the presence of antioxidant n-acetyl cysteine (1 mM). Salinomycin triggers cell membrane scrambling, an effect at least partially due to oxidative stress and entry of extracellular Ca 2+ .Salinomycin, a polyether ionophore antibiotic isolated from This study explored whether salinomycin triggers phosphatidylserine translocation to the erythrocyte surface. Moreover, the study addressed the cellular mechanisms involved. It is shown that salinomycin triggers erythrocyte cell membrane scrambling, an effect paralleled by and at least in part due to increase in [Ca 2+ ] i . Materials and MethodsErythrocytes, solutions and chemicals. Leucocyte-depleted erythrocytes were kindly provided by the blood bank of the University of T€ ubingen. The study was approved by the ethics committee of the University of T€ ubingen (184/2003 V). Erythrocytes were incubated in vitro at a haematocrit of 0.4% in Ringer solution containing (in mM) 125 NaCl, 5 KCl, 1 MgSO 4 , 32 N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid (HEPES), 5 glucose, 1 CaCl 2 ; pH 7.4 at 37°C for 48 hr. Where indicated, erythrocytes were exposed to salinomycin (Sigma-Aldrich, Freiburg, Germany) at the indicated concentrations. In Ca 2+ -free Ringer solution, 1 mM CaCl 2 was substituted by 1 mM glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA).FACS analysis of annexin-V binding and forward scatter. After incubation under the respective experimental condition, 50 ll cell suspension was washed in Ringer solution conta...

Aristolochic Acid triggers eryptosis, an effect at least in part due to entry of extracellular Ca(2+) and ceramide formation.

The peptide antibiotic and ionophore gramicidin has previously been shown to trigger apoptosis of nucleated cells. In analogy to apoptosis, the suicidal death of erythrocytes or eryptosis involves cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosis include oxidative stress, increase of cytosolic Ca2+ activity ([Ca2+]i), and ceramide. The present study explored, whether gramicidin triggers eryptosis. To this end phosphatidylserine exposure at the cell surface was estimated from annexin V binding, cell volume from forward scatter, red blood cell distribution width (RDW) from electronic particle counting, reactive oxidant species (ROS) from 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) fluorescence, [Ca2+]i from Fluo3- and Fluo4 fluorescence, and ceramide abundance from binding of specific antibodies. As a result, a 24 h exposure of human erythrocytes to gramicidin significantly increased the percentage of annexin-V-binding cells (≥1 µg/mL), forward scatter (≥0.5 µg/mL) and hemolysis. Gramicidin enhanced ROS activity, [Ca2+]i and ceramide abundance at the erythrocyte surface. The stimulation of annexin-V-binding by gramicidin was significantly blunted but not abolished by removal of extracellular Ca2+. In conclusion, gramicidin stimulates phospholipid scrambling of the erythrocyte cell membrane, an effect at least partially due to induction of oxidative stress, increase of [Ca2+]i and up-regulation of ceramide abundance. Despite increase of [Ca2+]i, gramicidin increases cell volume and slightly reduces RWD.

] i ) and loss of cellular K + foster apoptosis-like suicidal erythrocyte death or eryptosis, which is characterised by cell shrinkage and cell membrane scrambling leading to phosphatidylserine exposure at the erythrocyte surface. The present study explored whether nystatin stimulates eryptosis. Cell volume was estimated from forward scatter (FSC), phosphatidylserine exposure from annexin V binding and [Ca 2+ ] i from Fluo3-fluorescence in flow cytometry. A 48-hr exposure to nystatin (15 lg/ml) was followed by a significant increase of [Ca 2+ ] i , a significant increase of annexin V binding and a significant decrease of FSC. The annexin V binding after nystatin treatment was significantly blunted in the nominal absence of extracellular Ca 2+ . Partial replacement of extracellular Na + with extracellular K + blunted the nystatin-induced erythrocyte shrinkage but increased [Ca 2+ ] i and annexin V binding. Nystatin triggers cell membrane scrambling, an effect at least partially due to entry of extracellular Ca 2+ .